The present invention relates to a vacuum variable capacitor device that is used for various applications such as an oscillator of a high power transmitter, a high frequency power source of a semiconductor manufacturing device, a tank circuit of an inductive heating device.
FIG. 3 and FIG. 4 show, respectively, a longitudinal cross section and a partly enlarged section of a vacuum variable capacitor, according to Japanese Patent Unexamined Publication (refereed to as xe2x80x9cKokai Kohoxe2x80x9d in Japanese) No. 11(1999)273998 which is an equivalent for Japanese Patent Application No. 10(1998)0074755.
There is provided an insulated cylinder 1 made of an insulating material such as ceramic and the like. As is seen in FIG. 3, the insulated cylinder 1 has first and second ends, which are respectively, joined with a first cylinder 2a and a second cylinder 2b, to thereby form a cylindrical shape. The first and second ends of the insulated cylinder 1 are made of copper, and are blocked by means of, respectively, an immovable end plate 3 and a movable end plate 4, to thereby form a vacuum container 5. Inside the immovable end plate 3, there are provided a plurality of first cylindrical electrode plates F than range from F1 to Fn having different diameters. The first cylindrical electrode plates F1 to Fn stand on the inside of the immovable end plate 3, and are concentrically disposed at regular radial intervals, to thereby form an immovable electrode 6.
There is provided a conductor 7 for mounting a movable electrode 8. The conductor 7 is so disposed in the vacuum container 5 as to oppose the immovable end plate 3. On a first side of the conductor 7 facing the immovable end plate 3, there are provided a plurality of second cylindrical electrode plates M that range from M1 to Mn having different diameters. The second cylindrical electrode plates M1 to Mn stand on the first side of the conductor 7, and are concentrically disposed at regular radial intervals, to thereby form the movable electrode 8. Each of the second cylindrical electrode plates ranging from M2 to Mn is put and ousted from between adjacent two of the first cylindrical electrode plates F1 to Fn (interdigitation), while each of the first cylindrical electrode plates ranging from F1 to Fnxe2x88x921 is put and ousted from between adjacent two of the second cylindrical electrode plates M1 to Mn (interdigitation). There is provided a center pin 9 standing at an internal center of the immovable end plate 3. There is provided a movable guide 10 which is cylindrical and functions as a guide. The movable guide 10 also functions as a lead. The movable guide 10 is so disposed as to penetrate through a center of the conductor 7. The center pin 9 is inserted into the movable guide 10 in a slidable manner.
There is provided a bellows 15 having a first end which is mounted to the movable guide 10. The bellows 15 is cylindrical and retractable. Moreover, the bellows 15 is used for maintaining a vacuum condition and for energizing. The bellows 15 further has a second end mounted to an internal face of the movable end plate 4. There is defined an opening 4a in the movable end plate 4. The opening 4a is disposed on a radial inner side of the second end of the bellows 15. There is provided a nut receptacle 11 which is cylindrical, and stands around the entire circumference of the opening 4a on the internal face of the movable end plate 4. There is formed a collar 11a at an internal end of the nut receptacle 11. There is provided a screw shaft 12 having a first end which is connected to the movable guide 10. The screw shaft 12 also has a second end projecting into the nut receptacle 11 through the collar 11a. There is provided an adjuster nut 13 having a first end which is so supported to the collar 11a by way of a bearing 16 as to rotate arbitrarily. The first end of the adjuster nut 13 defines a screw shaft opening 13a so that the adjuster nut 13 is screwed down on the screw shaft 12. The second end of the screw shaft 12 defines a coaxial screw opening 12a. With the screw opening 12a, the screw shaft 12 is screwed down on an adjuster screw 14 having a screw head 14a. Moreover, the adjuster nut 13 has a large opening 13b adjacent to the screw shaft opening 13a. The large diameter opening 13b is larger in diameter than the screw shaft opening 13a. There is defined a stage 13c between the screw shaft opening 13a and the large diameter opening 13b. 
Described below is how to assuredly maintain a maximum electrostatic capacity of the vacuum variable capacitor having the constitution as mentioned above, and to facilitate adjustment of the maximum electrostatic capacity: At first, turn the adjuster nut 13 slightly clockwise (for right handed screw) so as to shift the screw shaft 12 slightly lower than a position X (not shown) of the maximum electrostatic capacity (at the position X, a lower end of the center pin 9 abuts on an upper end of the screw shaft 12), to thereby adjust the maximum electrostatic capacity to its predetermined value. The slight adjustment depends on the variation of the electrostatic capacity of the vacuum variable capacitors. Then, screw the adjuster screw 14 into the screw opening 12a to such an extent that the screw head 14a abuts on the stage 13c. Thereafter, fix the adjuster screw 14 to the screw shaft 12 by means of an adhesive and the like. Thereby, even if the adjuster nut 13 is likely to make a counterclockwise turn at the position X of the maximum electrostatic capacity, the screw head 14a of the adjuster screw 14 abuts on the stage 13c. Consequently, this can prevent the adjuster nut 13 from making the counterclockwise turn. Therefore, the screw shaft 12 cannot go up beyond the position X of the maximum electrostatic capacity. With this, the maximum electrostatic capacity can be assuredly maintained, and the adjustment of the maximum electrostatic capacity can be facilitated.
On the contrary, described below is how to arbitrarily variably adjust the electrostatic capacity of the vacuum variable capacitor having the constitution as mentioned above:
At first, turn the adjuster nut 13 so as to move the movable electrode 8 upward and downward by way of the screw shaft 12 and the movable guide 10. With this, a total area of the movable electrode 8 opposed to the immovable electrode 6 is varied, to thereby arbitrarily variably adjust the electrostatic capacity. With the center pin 9 and the movable guide 10 provided for constituting a guide mechanism, the movable electrode 8 can be moved stably, and a withstand voltage as well as the electrostatic capacity can show stabilized characteristics.
In the above mentioned related art, the movable guide 10 is integrated with a movable lead. Contrary to this, however, the movable guide 10 can be separated from the movable lead. Moreover, the movable guide 10 is to be electrically insulated from the center pin 9. The first end of the bellows 15 can be mounted to the conductor 7, instead of the movable guide 10.
When using the above vacuum variable capacitor for matching impedance of the semiconductor thin film manufacturing device, an operator needs to use a constitution shown in FIG. 5 for the following reason: Since a load changes continuously, it is necessary to carry out the impedance matching of the vacuum variable capacitor following the load change. More specifically, as is seen in FIG. 5, a vacuum variable capacitor 19 is mounted horizontally on a mounting base 17 by way of a pair of mounting plates 18, and a driving portion 21 is also mounted horizontally on the mounting base 17 by way of a mounting plate 20. A rotational shaft 22 of the driving portion 21 is coupled with the adjuster nut 13 by way of a coupling member 23. Driving the driving portion 21 allows the adjuster nut 13 to turn clockwise and counterclockwise, to thereby vary the electrostatic capacity of the vacuum variable capacitor 19.
FIG. 6 shows a general matching circuit using the vacuum variable capacitor 19 shown in FIG. 5. In the matching circuit, there are also provided a high frequency power source 24, a coil 25, and a load 26. It is necessary to insulate the immovable side from the movable side of the vacuum variable capacitor 19. Therefore, the vacuum variable capacitor device shown in FIG. 5 has a constitution in which each of the mounting plate 18 and the coupling member 23 is made of insulating material. For such insulation purpose, the coupling member 23 is continuously provided even when the coupling member 23 is not necessary. This ends up complicating the constitution of the vacuum variable capacitor device, and causing a backlash and the like. Thereby, it is difficult to control the driving portion 21.
It is therefore an object of the present invention to provide a vacuum variable capacitor device that does not require a coupling member, to thereby simplify a constitution of the vacuum variable capacitor device.
It is another object of the present invention to prevent any backlash from occurring, to thereby facilitate control of a driving portion of the vacuum variable capacitor device.
According to a first aspect of the present invention, there is provided an adjuster nut rotatably supported to a vacuum container of a vacuum variable capacitor of a vacuum variable capacitor device. The adjuster nut comprises a nut portion, and a shank made of an insulating material. The shank has a first end integrated with the nut portion and a second end adapted to be directly coupled with a rotational shaft of a driving portion of the vacuum variable capacitor device.
According to a second aspect of the present invention, there is provided an adjuster nut rotatably supported to a vacuum container of a vacuum variable capacitor of a vacuum variable capacitor device. The adjuster nut comprises a deformable bellows, a nut portion, and a shank. The bellows has a first end, and a second end opposite to the first end. The nut portion has a first end, and a second end coupled with the first end of the bellows. The shank which is made of an insulating material has a first end coupled with the second end of the bellows, and a second end adapted to be directly coupled with a rotational shaft of a driving portion of the vacuum variable capacitor device.